A study of gene expression in chickens, frogs, pufferfish, mice and people has revealed surprising similarities in several key tissues. Researchers have shown that expression in tissues with a limited number of specialized cell types is strongly conserved, even between the mammalian and non-mammalian vertebrates.

Timothy Hughes from the University of Toronto, Canada, worked with a team of researchers to investigate evolutionary alterations in gene regulation in the five different vertebrates. They found that although the specialized DNA sequences that regulate the expression of the genes seem to have changed beyond recognition over the hundreds of millions of years since the clades parted evolutionary company, the actual patterns of gene expression remain closely conserved.

According to Hughes, “There are clearly strong evolutionary constraints on tissue-specific gene expression. Many genes show conserved human/fish expression despite having almost no nonexonic conserved primary sequence.”